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TPS1689: TPS1689: Minimum output capacitance

CNH
Prodigy 30 points
Part Number: TPS1689

Tool/software:

To whom it may concern,

The datasheet lists in section 5.3 a minimum C.out of 10 uF, but is it possible to use less? There are some applications where the output capacitance must be minimized for hot-swap. Is it possible to use a minimum putout capacitance of 1.0 uF?

Thank you in advance

  • 0
    TI__Guru* 79111 points

    Yes . That should be fine.

    Regards 

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Hi, Kunal:

    Could you please update the datasheet? Is there a technical reason for minimum output capacitance for an ECB/hotswap controller? If not, could the datasheet be updated?

    We need this updated because this limitation restricts this part's use in our application. We would like to use it in applications where the output capacitance is 1.0 uF minimum.

  • 0 in reply to CNH
    TI__Guru* 79111 points

    Hi CNH,

    Output capacitance is not required for device to work and is not part of EC table . It is a recommendation and not a guarantee so you should also consider it like this. 

    We have given 10uF as a general number after considering wide number of applications. Output cap prevents VOUT -ve drop. So higher cap, lesser is VOUT -ve.

    Regards

    Kunal Goel

  • 0
    Prodigy 30 points

    Hi, Kunal:

    So the datasheet will be updated?

  • 0
    Prodigy 30 points

    Hi, Kunal:

    So the datasheet will be updated?

  • 0 in reply to CNH
    TI__Guru* 79111 points

    Datasheet update is not needed as i clarified earlier. 

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Hi, Kunal:

    If the supporting documentation is not update, then we cannot use the part in our project. If you cannot update the datasheet, can you provide a formal statement?

    Thank you,

    David

  • 0 in reply to CNH
    TI__Guru* 79111 points

    Hi David,

    Please let me check on this and get back ASAP.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru* 79111 points

    Hi David,

    Up on further checking with the design, our designer recommended min 10uF at the output for this device to limit the slew rate at output during transient events. Please follow as per the current datasheet to avoid any risk to the device.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Hi, Kunal:

    The transient nature of the load should be the system designer's determination. I believe that the slew rate for the TPS1689 is adjustable. Because of this, why would there even be a minimum capacitance limit? Why is this?

    If this 10 uF recommendation is to limit the TPS1689 slew rate, then I may have to design this component out of the design, and this is a volume of 50k units/annum. However, if the TPS1689 cannot work with 10 uF minimum, then it cannot work in the design.

    Thank you,

    CNH

  • 0 in reply to CNH
    TI__Guru* 79111 points

    Hi David,

    Sorry . But I did not meant that. I am not talking about VOUT slew rate during turn on of eFuse.

    During events like short circuit at output when current is suddenly cut off then VOUT can go -ve beyond abs max rating of VOUT pin and can cause damage to device. 

    Ceramic cap at output helps in reducing slew rate of VOUT falling and thus it will go less -ve. So we recommend minimum 10uFcap at output to limit VOUT, -ve voltage during events like short at output, overcurrent .

    Below link has more details on pg 21. 

    Analog Design Journal - Issue 1, 2025

    Regards

    Kunal Goel

  • 0
    Prodigy 30 points

    Hi Kunal:

    Does the note in the journal account for the Schottky diode? When I read the journal, it said the measurements did not include capacitance and the Schottky diode. Wouldn't the Schottky diode, which is very fast, mean that very little output capacitance is required?

    CNH

  • 0 in reply to CNH
    TI__Guru* 79111 points

    Hi CNH,

    Can you please share screenshot of the note?

    It is true if you have schottky diode at output you need less cap at output for preventing VOUT going -ve.

    Regards

    Kunal Goel